Spectral Model for Crowd Walking Load

Abstract

Crowd walking is a common daily activity that can cause large vibrations on slender structures such as footbridges and long-span floors. Although modeling of crowd walking loads is critical in structural response prediction, this type of modeling is considered difficult due to the randomness in pedestrian walking gaits, temporal-spatial variation of walking procedures, and technical difficulties in crowd walking experiments. The authors developed a spectral model for crowd walking. First, the auto-power spectral density (PSD) function of an individual was adopted from a previous study. Inspired by research in earthquake engineering, the cross-power spectral density of every two persons in a crowd was developed, consisting of coherence functions and auto-PSDs. Coherence function parameters were proposed separately from experimental records for three pedestrian densities: unrestricted, restricted, and exceptionally restricted traffic conditions. After obtaining a PSD matrix for crowd walking, the structural responses could be predicted by the stochastic vibration theory. The feasibility of the model was verified by comparing the measured responses of a model footbridge with the prediction responses from the proposed spectral model.